Temperature controlled semiconductor processing chambers are used for depositing various material layers onto a substrate surface or surfaces. In processing substrates within the processing chamber, one or more substrates or workpieces, such as silicon wafers, are placed on a workpiece support within the processing chamber. Both the substrate and workpiece support are heated to a desired temperature. In a typical processing step, reactant gases are introduced into the processing chamber and passed over each heated substrate, whereby a chemical vapor deposition (CVD) or an atomic layer deposition (ALD) process deposits a thin layer of the reactant material in the reactant gases on the substrate surface(s). Through subsequent processes, these layers are formed into integrated circuits, and tens to thousands or even millions of integrated devices, depending on the size of the substrate and the complexity of the circuits, are cut from the processed substrate.
Various process parameters must be carefully controlled to ensure the high quality of the resulting deposited layers. One such critical parameter is the temperature of the substrate during each processing step. During CVD, for example, the deposition gases react at particular temperatures to deposit the thin layer on the substrate. If the temperature varies greatly across the surface of the substrate, the deposited layer could be uneven. Accordingly, it is important that the substrate temperature be stable and uniform at the desired temperature during processing of the substrate. Similarly, non-uniformity or instability of temperatures across a substrate during other thermal treatments can affect the uniformity of resulting structures on the surface of the substrate. Other processes for which temperature control can be critical include, but are not limited to, oxidation, nitridation, dopant diffusion, sputter depositions, photolithography, dry etching, plasma processes, and high temperature anneals.
Methods and systems are known for measuring the temperature at various locations near and immediately adjacent to the substrate being processed. Typically, thermocouple assemblies are disposed at various locations near the substrate being processed, and these thermocouple assemblies are operatively connected to a controller to assist in providing a more uniform temperature across the entire surface of the substrate. For example, U.S. Pat. No. 6,121,061 issued to Van Bilsen generally teaches a plurality of temperature sensors measuring the temperature at various points surrounding the substrate, including a thermocouple assembly placed near the leading edge of the substrate, another near the trailing edge, one at a side, and another below the substrate near the center of the substrate.
A problem often associated with the replacement of thermocouple assemblies, either because of failure or for regular maintenance, is the variability between each thermocouple assembly. The variability between each thermocouple assembly may be due to any number of factors including, but not limited to, materials used or the methods for producing the thermocouple assemblies. The variability of each thermocouple assembly may result in varying temperature measurements, or a different temperature measurement at the same temperature relative to a previous thermocouple assembly, which in turn may affect the deposition process if the measured temperature is substantially different than the actual temperature within the reaction chamber. Because the temperature control system is based on the calibrated temperature measured by each thermocouple assembly connected to the system, any variability of the calibration between successive thermocouple assemblies will cause variations in the temperature control scheme that may lead to non-uniform deposition of layers on the substrates.
A need therefore exists for a temperature measuring device that includes pre-calibrated parameters such that the deposition tool can be automatically adjusted to account for the pre-calibrated parameters of the temperature measuring device. A need also exists for a temperature measuring device in which pre-calibrated parameters are integrally included with the temperature measuring device.